Background:

For many years astronomers have sought to locate the most distant
objects in the Universe. As light travels at a finite speed, we see
back in time and the most powerful facilities, such as the Keck
Telescopes in Hawaii and Hubble Space Telescope, can readily glimpse
sources viewed when the Universe was only a billion years old.
However, only the most spectacularly luminous objects are normally
detectable at these vast distances. For many reasons, astronomers seek
to find more representative objects at early times. Finding the
earliest sources, forming stars for the first time, is currently
a major goal in cosmology. However, most astronomers believe
these will be faint low mass clusters of, at most, a few million stars.
As such they lie beyond reach of current facilities. Locating and
characterizing this primeval population is a major motivation for
constructing Hubble's successor,
the Next Generation Space Telescope (NGST) , a 6.5 meter telescope
to be launched in 2009.

Magnifying Faint Objects via Gravitational Lensing:

Gravitational lensing , a feature of Einstein's theory
of General Relativity, offers a unique short cut to solving this
problem while we wait for NGST to be launched. By viewing
the deep universe through a foreground massive cluster, faint
background sources can be magnified by factors of as much as 50
by foreground structures. The breakthrough in our article is that
we believe we have secured a first glimpse of this predicted
population of faint star-forming systems at early times. Continued
work in this direction using the Keck telescopes will give astronomers
valuable information on how best to exploit NGST and provide the
first constraint on when the first stars in the Universe formed.

First Light Viewed Through the Rich Cluster Abell 2218

So far we have found 3 promising examples in our survey but the most
distant, at a redshift 5.6 (corresponding to 13.4 billion light
years distance in current cosmological models), is the most intriguing.
We found this source magnified by the foreground cluster
Abell 2218. This is a stunning cluster with many lensed
`arc-like' features of known redshift. Such data,
gathered by our team, has enabled us to determine very precisely where
the regions of maximum magnification occur. By
scanning this area we encountered the source which forms the basis
of our recent article.
We discovered a
pair of images which represent the magnified result of a single
source whose light is magnified 30-fold and thus would
ordinarily (without the lensing boost) be undetectable except with the
future Next Generation Space Telescope. The
Keck spectra show both images arise from the same source, which is
actively forming stars but, crucially, those stars have not yet
aged sufficiently to form a mature underlying population. In short,
the object is being viewed less than 1 billion years after the Big Bang
but is only about a million years old. This makes it a promising
candidate for a primeval star cluster, possibly one of many at
that time, which subsequently merge and assemble to form the
large bright galaxies we see today.